This study is designed to examine the problems of organ and cellular function and survival after organ storage. We have been studying the cellular changes especially as they relate to nuclear function and nucleic acid metabolism during and after storage. The main areas of concentration include the chromatin template, and the intact nature of DNA, the RNA polymerases and the cellular content of the purine nucleotides which provide the energy for driving a viable system. This past year, we looked at the single-stranded nature of DNA breaks which occur. Utilizing an alkaline sucrose gradient and following the DNA fluorometrically, we found that breaks became evident after 30 minutes of warm storage or after four hours of cold storage and increased with time. To further define these breaks we used S1 nuclease to examine the single-stranded regions. We found that the major pathway of purine catabolism in mouse kidney during storage is through IMP, inosine, hypoxanthine and xanthine. Short periods of ischemia followed by a restoration of blood flow allowed a rapid return of the energy charge to control values and a return of ATP and GTP to 50 to 70 percent of control values and then a slow return to 100 percent of control values. Long periods of warm ischemia greater than 60 minutes, were followed by the return of the energy charge to control values after restoration of blood flow, but adenine and guanine nucleotides never recovered. The intra-cellular solutions, Collins' or Sacks' maintain the adenine nucleotide level better than saline.